In recent years, composite materials in which carbon nanotubes (hereinafter, also referred to as “CNTs”) are compounded with an elastomer, such as a rubber, have been attracting interest as materials that have excellent heat resistance and mechanical properties.
For example, PTL 1 discloses, as a composite material having excellent heat resistance and mechanical properties, a crosslinked rubber that is obtained through crosslinking of a crosslinkable rubber composition containing a hydrogenated carboxylated nitrile rubber, a crosslinking agent formed by a peroxide, and CNTs.